This application seeks funding for the development of a non-invasive bed side monitor of pulmonary arterial pressure in infants. The principle of operation is derived from earlier non-invasive research on humans and from invasive studies on dogs, in which an improved method of non-invasive detection of the time of closure of the aortic and pulmonary valves has been developed. The technique depends on the detection of subtle but distinct movements of the chest wall overlying the heart, said movements resulting from the forces created by closing and tensing of these valves. Since the time interval separating the closure of these two valves is known to depend on the level of pulmonary arterial pressure, the application of this technique to the problem of non-invasive assessment of pulmonary hypertension is a natural extension of this technology. The technique causes no danger or discomfort to the child, and does not interfere with his/her care or treatment. Pulmonary hypertension is a central factor in pathogenesis of Persistent Fetal Circulation and may be a complicating factor in Respiratory Distress Syndrome. It is also a very serious complication of congenital malformations such as Patent Ductus Arteriosus. If this research is successful, a practical non-invasive bed side monitor of pulmonary arterial pressure will result, which will be simple and inexpensive so as to be useful even in small hospitals. The instrument would appear to have wide ranging commercial applications. The instrument can be operated by nursing personnel. The technique will complement the recently developed transcutaneous oxygen monitoring instrumentation, and will significantly expand the scope of information available non-invasively to the physician in the neonatal intensive care unit.